Electric control circuit



April 10, 1945.

O. W. LIVINGSTON ELECTRIC CONTROL CIRCUIT Filed Feb. 15, 1945 l to a:Inventor:

Orrin W Livingston,

His Attorney.

Patented Apr. 10, 1945 UNITED STATES- iATENT OFFICE ELECTRIC CONTROLCIRCUIT Orrin W. Livingston, Scotia, N. Y., assignor to General ElectricCompany, a corporation of New York Application February 15, 19-43,Serial No. 475,878

10 Claims.

closely regulated at the different levels which are pre-established byadjustments which are readily made.

It is an object of my invention to provide a new and improved electriccontrol circuit.

It is another object of my invention to provide a new and improvedelectric regulating system.

It is still another object of my invention to provide a new and improvedcircuit for maintaining an electrical condition of a load circuit atdiiierent levels during successive time intervals and for regulating theelectrical condition during each of the intervals to maintain the con--dition at the desired value independentl of variations in supply circuitvoltage or in the magnitude of the load impedance.

In the illustrated embodiment of my invention, a load circuit such asthe filaments of a plurality of electric valves is energized by apreestablished pattern of voltage from an alternating-current supplycircuit. A control system for effecting the energization of a loadcircuit in accordance with a predetermined time pattern from analternating current circuit is described and claimed in copending Bivensapplication Serial No. 460,240, filed September 30, 1942, and assignedto the assignee of the present invention. The disclosure of the Bivensapplication is prior art with respect to my invention. The voltageimpressed on the load is controlled by a saturable inductive deviceconnected between the supply and load circuits and having aunidirectional magnetizing winding energized from thealternating-current supply circuit through a controlled electric valve.The control voltage for the electric valve is regulated in accordancewith the voltage of the load circuit and the settings of a plurality ofadjustable resistors which are selectively connected in circuit with aregulating electric valve of the emission-limited type to control theratio between the voltage of the load circuit and the voltage impressedon the cathode of the regulating valve and thereby to establish thevoltage levels impressed on the load circuit during dinerent periods ofthe load-voltage pattern. Suitable timing devices are employed foreffecting the selective connections of the impedance elements with thecathode of the emission-limited regulating electric valve. A controlsystem including an emission-limited electric valve for regulating thecurrent supplied to a load circuit during timed intervals is describedand claimed in the copending Cooper application Serial No. 480,150,filed March 23, 1943, and assigned to the assignee of the presentinvention. This Cooper application is a continuation-in-part of Gooperapplication Serial No. 423,526, filed December 18, 1941, and assigned tothe assignee of this application. The above Cooper applications areprior art with respect to my invention.

My invention will be better understood by reference to the followingdescription taken in connection with the accompanying drawing and itsscope will be pointed out in the appended claims. In the drawing, Fig. 1is a schematic representation of one embodiment of my invention and Fig.2 diagrammatically illustrates certain operating conditions of thesystem shown in Fig. 1.

In the drawing, I have shown my invention embodied in a system formaintaining the filaments of electric valves at different voltage levelsduring successive time intervals during what is called an aging process.As illustrated in the drawing, the filaments it of electric valves IIare connected in parallel across the terminals of a secondary winding l2of a transformer l3 having the primary winding M thereof energized froman alternating current supply circuit I5 through the alternating-currentwinding [6 of a saturableinductive device ll. The device H is providedwith a control winding l8 which is variably energized to control theimpedance thereof and thereby control the voltage impressed on thetransformer [13. Manually operable switches l9 and 2B are connected inseries with the supply circuit. A source of alternating-current controlvoltage is provided by a transformer 2| having the primary winding 22thereof connected with the conductors of the supply circuit i5 betweenthe switches l5 and 20, so that the transformer 21 is energized as soonas the contacts of switch it are closed. The secondary winding 23 oftransformer 2i energizes the conductors 24 and 25' which provide acontrol-voltage bus. A con-r ductor 25a is connected with the sameterminal of the winding 23 as conductor 25 through the normally opencontact 26 of switch 20.

The control winding it of the saturable inductive device I! is connectedin series with an electric valve 27 and across the conductors 24 and25a. As illustrated in the drawing, the valve 21 is preferably'of thetype utilizing an ionizable medium, such as a gas or vapor, andcomprises an anode 28, a cathode 29, a heater element 35, and a controlmember or grid 3%. The heater element is energized b a transformersecondary winding 32 of a transformer 33 havin the primary winding 3:3thereof energized from the conductors 2t and 25. Secondary windings 3'5and 35, of the'transformer 33 provide voltage supplies for energizingthe control member SI of electric valve 2'! and the secondar winding 31provides a voltage for energizing the heater element 38 of anuncontrolled electric discharge valve 39 which is connected in serieswith a resistor 40 and across the terminals of the control winding is ofthe saturable inductive device ii. The valve 39 is oppositely poled withrespect to the valve 21 and winding it to conduct current during thehalf cycles that electric valve 21 is nonconducting and, in this way, toprovide for the flow of current through winding l8 resulting from thedecay of flux in the associated core.

In order to control the conductivity of electric valve 27 and, in thisway, to control the energization of the winding I8, I provide means forimpressing on the control member 3| a plurality of voltage components,at least one of which is reg-. ulated in accordance with a condition ofthe load and which is adjusted in steps at predetermined intervals tochange the level of the load condition in accordance with apreestablished pattern. Referring now to the drawing, the transformerwinding 36 is provided with an intermediate torminal which is connectedwith the'cathode of electric valve 21. A capacitor All and resistor 42are connected in series across the terminals of the transformer winding36 and provide means for shifting the phase of the voltage between theintermediate terminal of the winding 36 and the common terminal 43 ofcapacitor 4| and resistor provide means, for varying the instant ofignition of electric valve 21 as is well understood. The circuits forenergizing these elements will now be described. Resistor 45 isconnected in series with a resistor 59 and across the terminals of acapacitor 50, which is connectedto be charged from the secondary winding35 of transformer 33 through a resistor 5| and a unilaterally conductingdevice 52 of any suitable type and which, as illustrated, comprises atwo-element electric discharge valve. The voltage acrossseries-connected resistors 45 and 49 is impressed on a circuit includingin series resistors 53 and 54 and capacitor M. In order to control thevoltage, of capacitor 4'! with respect to the voltage across resistors45 and $9, I provide an electric valve 55 having the anode,- cathedecircuit connected in parallel with capach tor 4! and resistor 54 inseries. The electric ;valve 55 is of the controlled type and, asillustrated, is of the type employing a filamentary I cathode which isvariably energized to control the impedance of the valve. The valve 55may be termed an emission limited regulating valve.

' One terminal of the filament cf the valve 55 is cQnnected directlywith one side of the load cir-v cuit by a conductor 56. The otherterminal of The voltages appearing the filament is connected to aconductor 51 which is arranged to be connected to the other side of theload circuit through a conductor 58 and one or more resistance elementswhich are selectively connected in the circuit at different times to esrtablish the level of voltage to be maintained across the load circuit.As illustrated in the drawing, resistance elements 59 are permanentlyconnected between conductors 51 and 58' and are provided with adjustingmeans 60. Resistances 6i; and 62, also provided with adjusting meanstil, each have one terminal connected with conductor- 5'! and the otherterminals arranged to be connected with the conductor 58 under thecontrol of contacts 63. and 64, respectively. As illustrated, contact 63is part of a relay 65 having an operating coil 65v and including alsocontacts 51 and 58. The contact 64 is the normally closed O Atact of arelay 69 having an operating coil 10 connected to be energized from thecontrol-voltage supply lines 24 and- 25a under the control of a switchH. The contacts 63 and G l are controlled to change the ratio of thevoltage impressed on the cathode of electric valve 55 with respect tothe load voltage at predetermined times in the pattern of load voltageby the relays 55 and 59 as will be described in more detail at a laterpoint in the specification in connection with the operation of thesystem as a whole.

The resistor 64 which, as previously mentioned, is utilized to impress aunidirectional voltage on the control member of electric valve 21 isenergized by a transient voltage responsive to the voltage of the loadcircuit. As illustrated in the drawing, a unilaterally conducting device12, such as a gaseous-discharge electric valve, is connected with theanode-cathode circuit thereof in series with resistor 44, a capacitor13, the secondary 5 winding l of a transformer 15, and a resistor 76..The primary winding 11 of the transformer 15 is connected across theconductors 56 and 58 to energize the transformer in accordance with theload voltage. A resistor 78 and a Capacitor 19 are connected in paralleland across resistor 44 and capacitor 13. Means for discharging, thecapacitor 13 is provided by a circuit shunting the capacitor andincluding a discharge resistor 80 and the normally closed contact 81 ofa relay 82 having an operating coil 83., The relay 82 has a normallyclosed contact 84 which controls a discharge circuit for capacitor 4'!including a discharge resistor 85.

The energizing circuit for the operating coil 83 of relay 82 iscompleted from'the conductor 24 to the conductor 2511 through a normallyclosed contact 86 of a relay 8'! having an operating coil 88 arranged tobe energized from the controlvoltage supply lines 24 and 25a through aswitch 89. As illustrated, the relay 8! also includes a normally opencontact 90 which establishes a circuit from conductor 25a to conductor24 through the operating coil 66 of relay 65, and the normally closedcontact 9! of a, relay 92. The relay 92 is preferably a voltageresponsive relay which is energized in accordance with the load circuitvoltage and which picks up at a voltage somewhat more than the voltageof the load circuit to be maintained durin'g'the first period of theload voltage pattern but less than the voltage to be maintained duringone of the subsequent periods of the pattern.

A, better understanding of the illustrated em? bodiment of my inventionmay be had by a brief consideration of the operation thereof, referencebeing had to Fig. 2 in which the operative positions of the relays withrespect to the load-voltage cycle is illustrated. When the relay is inoperated position, the line illustrating the relay is offset upwardly.Each line is designated by the numeral designating the correspondingrelay in Fig. 1. Let it be assumed that the supply circuit i5 isenergized and the switch [9 closed. Under these conditions, thetransformer 2| is energized which, in turn, energizes the heaterelements of electric valves 21 and 39, The heater elements for electricvalves 52 and 12 have not been shown connected but it will be assumedthat these are also energized when transformer 23 is energized. If,after the valves are at operating temperature, it is desired to initiatethe energization of the load circuit with a pattern of voltage which hasbeen preestablished by the adjustment of the sliders 69 on the resistors59, 6|, and 62, the switch is closed and the load circuit is energizedthrough the winding [8 of the saturable inductive device l1. At theinstant of closure of switch 29, there is no unidirectional currentthrough the control winding l8 so that the impedance of the winding I5is at a maximum and the load voltage is substantially zero. The currentthrough the winding H3 at this time is maintained at zero by electricvalve 2! which is maintained nonconductive by the lagging component ofalternating-current voltage and the negative voltage of resistor 46which are impressed on the control member 3! thereof. When switch 29 isclosed, contact 26 is closed to energize the conductor aand complete acircuit'for the winding 83 of relay 82 through the contact 86 of relay81. Time-delay relays 69 and 8'! are also energized from conductors 24and 25a, assuming that switches H and 89 are in closed position.Operation of relay 82 opens contacts Bi and 84 and opens the dischargecircuits of capacitors l3 and 41. As soon as contacts BI and 84 open,capacitor 13 starts to charge through resistor 44 and capacitor 41starts to charge through resistors 53 and 54 and gradually to increasethe net positive component of unidirectional voltage impressed oncontrol member 3| of electric valve 21 to increase the current conductedby control winding l8 and, in this way, gradually increase the voltageimpressed on the load circuit, as shown at A on the load-voltage curveof Fig. 2. At some time during this increase of voltage, the relay 92picks up to open contact 9| for a purpose to be described hereinafter.As the load voltage increases, a transient voltage opposing the increasein voltage is impressed on the control member 3! by means of resistor44. This voltage is derived from the transformer 75 and has anexponential characteristic dependent upon the charging rate of capacitor13. After the load voltage has reached a steady value, the capacitor 13becomes fully charged and the voltage of resistor 44 reduces to zero.The voltage of resistor 44 acts as a stabilizing or antihunting voltageto prevent overshooting of the load voltage and also functions alongwith the voltage of capacitor 47 to delay the intial build-up of currentin the load circuit.

As soon as the load circuit is energized, the voltage thereof isimpressed on the cathode of the electric valve 55 through resistors 59and 82 in parallel. The magnitudes of these resistors determine theratio of the voltage of the load circuit and the voltage impressed onthe cathode of electric valve 55 and, as a result, determine the voltageof the load circuit which the regulator circuit will maintain. If thevoltage of the load desired value.

circuit tends to increase above that for which the regulator is set, theenergization of the cathode of valve 55 is increased, which reduces theimpedance oi the valve and decreases the positive voltage impressed onthe control member 3| by capacitor 41. This decreases the conductivityof valve 21 and, as a result, increases the impedance of device I! andrestores the load voltage to the If the load voltage tends to de-'crease below the preset value, the converse of this action takes placeand the current through the control winding I8 is increased to reducethe impedance of the device I! and, as a result, restore the voltage ofthe load circuit. From the above, it is seen that the load voltage isregulated at the preestablished value regardless of supply circuitvoltage fluctuations or changes in load impedance, A predetermined timeafter closure of control 21, the relay 69 is operated to open contacts54 and remove the resistor 62 from the circuit of the cathode ofelectric valve 55. Inasmuch as resistors 62 are in parallel withresistors 59, the removal of resistors 52 increases the impedance incircuit with the cathode of valve 55 so that a higher load voltage isrequired for a. given energization of the cathode of valve 55. In thisway, a higher level of voltage is maintained during the second period ofload circuit, voltage illustrated at B in Fig. 2. A predetermined timeafter closure of contact 21, the time delay relay 81 operates toterminate the second period of load circuit voltage pattern. When relay8'! picks up, contacts 86 open, thus deenergizing the operating coil ofrelay 82. This closes contacts 84 to estab- T lish the discharge circuitfor the capacitor 41 and render the electric valve 21 nonconductive.This allows the load voltage to decrease until relay 92 drops out which,as previously mentioned, is preferably slightly below the load voltageto be main! tained during the third period of the load-voltage pattern.The load voltage drops suddenly, as illustrated at C in Fig. 2, duringthe period that electric valve 2'! is maintained nonconducting and, assoon as relay 92 drops out, relay 65 is energized from conductors 24 and25a through contact 9! of relay 92 and contact of relay 51. Operation ofrelay 65 closes contacts 63 to connect resistors 50 and SI in parallelin the circuit of the cathode of electric valve 55 and establishes thevoltage level to be maintainedduring the third period of theload-voltage pattern illustrated at D in Fig. 2. Operationof relay 65closes contacts 61 to seal in relay 65 and closure of contacts 68completes an energizing circuit for relay 82 to open the contacts BI and84 and return control to the regulator including electric valves 55 and21.

The seal-in contact 61 is only necessary in the event that the loadvoltage to be maintained during the third period of the voltage patternis high enough to pick up relay 92 and open contact 9|. The switchingsequence outlined above prevents the reduction of resistance in serieswith the cathode of valve 55 required for a lower load-, voltage levelfrom being accomplished until after the load voltage has been reducedbelow this level. This prevents damage to the regulatin tube 55 whichmight otherwise result. The drop in load voltage is accomplished bymaintaining valve 21 nonconducting until the load voltage falls belowthe level to be maintained during the third period of the load-voltagepattern. When the loadvoltage pattern is complete, switch 20 is openedand the system is reset for another operation. While time-delay relaysof the mechanical type gized during the periods 2 and 3, and relay 81isenergized during the third period only of the load voltage pattern.

In one application for which the illustrated embodiment of my inventionhas been employed, the

voltage during the first period has been maintained at 18 volts, duringthesecond period at 26 volts,.and during the third period at 13 volts.When the system is adjusted for these voltages, it has beenfounddesirable to have the relay 92 pick up at about 14 volts and to drop outat about 'volts. The relay must be capable of withstanding, the maximumvoltage of 26 volts.

From the foregoing description, it will be apparent that my inventionprovides a system which not only permits the energization of a loadcircuit in accordance with a preestablished pattern of voltage orcurrent but also maintains close regulation of the voltage during eachperiod of the voltage or current pattern. Protection of the regulatingtube is also provided when transferring from a higher to a lowerlevel'of load voltage. It will be apparent that the system of thepresent invention may be employed for regulating current or any otherdesired condition instead oi voltage.

While I have shown and described a particular embodiment of myinvention, it will be obvious to those skilled in the art that changesand modifications may be made without departing from my invention in itsbroader aspects, and I therefore aim in the appended claims to cover allsuch changes and modifications as fall within the true spirit and scopeof my invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. In combination, an alternating-current supply circuit, a loadcircuit, electric translating apparatus interconnecting said circuitsincluding a saturable inductive device having a control winding, anelectric valve including a control member for controlling theenergization of said control winding, and means for energizing thecontrol member of said electric valve to maintain an electricalcondition of said load circuit at predetermined different levels duringdifferent time intervals including timing means for establishing saidintervals and means energized from said load circuit for regulating saidcondition at each of said levels.

2. In combination, a load circuit, means for energizing said loadcircuit including electric translating apparatus, a control circuit forcontrolling said translating apparatus to maintain an electricalcondition of said load circuit at predetermined different levels duringsuccessive time intervals comprising an electric valve having a cathodeof the filamentary type and a circuit interconnecting said filament andsaid load circuit including a plurality of impedance elements and aswitching means, and means including timing means for effectingoperating said switching condition of said load circuit and theenergization of said filamentary cathode.

3. In combination, an alternating-current supply circuit, a loadcircuit, electric. translating apparatus interconnecting saidcircuits'including a saturable inductance device having a controlwinding, an electric valve including a control member for controllingthe energization of said control winding, a control circuit forcontrolling the energization of said control member to maintain anelectrical condition of said load circuit at a predetermined levelduring one time intermeans selectively to energize said cathode fromsaid load circuit through impedances of difierent magnitudes duringdifierent ones of said intervals to change the ratio between theelectrical val and at a difierent level at a second time interval, meansfor regulating said condition at each of said levels including anelectric valve having a cathode of the filamentary type, an em ergizingcircuit interconnecting said filament and said load circuit includingmeans for completing said energizing circuit during the first of saidintervals through an impedance of predetermined magnitude, and forcompleting said energizing circuit during said second interval throughan impedance of smaller magnitude, means for effecting an unregulatedchange of said electrical condition from the level maintained duringsaid first interval to substantially the level to be maintained duringsaid second interval before completing said energizing circuit throughsaid lower impedance to prevent damage to said filamentary cathode.

4. In combination, a load circuit, means for energizing said loadcircuit including electric translating apparatus, a control circuit forcontrolling sald translating apparatus to maintain an electricalcondition of said load circuit at a predetermined level during one timeinterval and at a different level during a second time interval, meansfor regulating said condition at each of said levels includinganelectric valve having a cathode of the filamentary type, an energizingcircuit interconnecting said filament and said load circuit includingmeans for completing said energizing circuit during the first of saidintervals through an impedance of predetermined magnitude and forcompleting said energizing circuit during said second interval throughan impedance of smaller magnitude, means for efi'ecting an unregulatedchange of said electrical condition from the level maintained duringsaid first interval to substantially the level to be maintained duringsaid second interval before completing said energizing circuit throughsaid lower impedance to prevent damage to said filamentary cathode.

5. In combination, a load circuit, means for energizing said loadcircuit, electric translating apparatus interconnecting said circuits, acontrol circuit for controlling said translating apparatus to maintainan electrical condition of said load circuit at a lower level during asubsequent time interval, means for regulating said condition at each ofsaid levelsincludlng an electric valve having a cathode of thefilamentary type, a circuit interconnecting said filament and said loadcircuit, means for completing said circuit during the first of saidintervals to energize said filamentary cathode with a voltage having apredetermined magnitude relative to the level of the electricalcondition of said load circuit during said one interval, means forsubsequently energizing said filamentary cathode with a voltage having ahigher value relative to the magnitude of the electrical condition ofsaid load circuit, during said subsequent interval, and means forpreventing operation of said last-mentioned means until said electricalcondition of said load circuit has been reduced to a value substantiallyas low or lower than the level of said condition to be maintained duringsaid subsequent period.

6. In combination, a load circuit, means for energizing said loadcircuit including electric translating apparatus, means for controllingsaid translating apparatus comprising an electric discharge devicehaving a grid, means for impressing a unidirectional voltage on saidgrid to control an electrical condition of said load circuit andcomprising a second electric discharge device having a filamentarycathode, means responsive to said electrical condition for energizingsaid filamentary cathode and for maintaining a predetermined value ofsaid electrical condition for a predetermined period, timing means forchanging the energization of said filamentary cathode to establish asecond predetermined value of said electrical condition for a secondpredetermined period, and timing means for changing the energization ofsaid filamentary cathode to establish a third predetermined value ofsaid electrical condition for a third predetermined period.

'7. A control circuit for controlling an electrical condition of a loadcircuit comprising an electric discharge device having a grid, a secondelectric discharge device of the type including a filamentary cathodefor impressing a unidirectional voltage on said grid, means responsiveto said electrical condition for controlling the energization of saidfilamentary cathode and for maintaining said electrical condition at apredetermined value for a predetermined period of time, means forchanging the energization of said filamentary cathode to maintain saidelectrical condition at a second predetermined value for a secondpredetermined period of time, and means for changing the energization ofsaid filamentary cathode to maintain a third predetermined value of saidelectrical condition for a third period of time.

8. In combination, an alternating current supply circuit, a loadcircuit, means for controlling an electrical condition of said loadcircuit comprising an electric discharge device having a grid, a secondelectric discharge device of the type including a filamentary cathodefor impressing a unidirectional voltage on said grid, means responsiveto said electrical condition for controlling the energization of saidfilamentary cathode and for maintaining said electrical condition at apredetermined value for a predetermined number of cycles of voltage .ofsaid supply circuit, and means for changing the energization of saidfilamentary cathode to maintain said electrical condition at a secondpredetermined value for a second predetermined number of cycles ofvoltage of said supply circuit.

9. In combination, a load circuit, mean for energizing said load circuitincluding electric translating apparatus, means for controlling saidtranslating apparatus comprising an electric discharge device having agrid, means for impressing a unidirectional voltage component on saidgrid in response to a predetermined electrical condition of Said loadcircuit and including a second electric discharge device of thefilamentary cathode type wherein the cathode is variably energized inresponse to said electrical condition, means for impressing analternating component of voltage on said grid, initiating means forinitiating energization of said load circuit including means forimpressing said unidirectional component of voltage on said grid, andreactive means connected with said grid for delaying the rise of voltageof said grid due to said unidirectional component to effect the gradualapplication of voltage to said load circuit.

10. In combination, a load circuit, means for energizing said loadcircuit including electric translating apparatus connected between saidcircuits and comprising an electric discharge device having a grid,means for impressing an alternating component of voltag on said grid,means for impressing a unidirectional voltage on said grid andcomprising a second electric discharge device having a filamentarycathode, means responsive to an electrical condition of said loadcircuit for energizing said cathode to vary said unidirectional voltageand thereby maintain a predetermined characteristic of said condition,mean for initiating energization of said load circuit including meansfor establishing said unidirectional component of voltage, and meansconnected to said grid for controlling the rate of rise of the voltageimpressed on said grid to advance gradually the instant of initiation ofconduction of said discharge device and thereby to effect the gradualapplication of voltage to said load circuit.

ORRIN W. LIVINGSTON.

